1. Field of the Invention
This invention relates to an improved automated carcass splitting apparatus for use in animal slaughterhouses abattoirs and the like.
2. Background Discussion
Previously known devices for handling and splitting animal carcasses have comprised a wide variety of automated or semi-automated systems which are generally suitable for handling one specific type of beast or beasts of similar dimensions and characteristics i.e. beef and horse carcasses or pig and sheep carcasses. Amongst the splitting saws hitherto available have been electrically operated circular saws, electric or hydraulic reciprocating saws, band saws or pneumatic percussion cutters. Generally speaking, electric circular saws are preferred for splitting beef carcasses while a pig carcass splitter may often comprise pneumatically driven dual chopping blades driven down either side of the backbone. A reciprocating saw fitted with chopping blades has found limited acceptance as a splitter suitable for a wider range of animal carcasses.
In general the electric circular saw has been found to be the most suitable carcass splitting saw in view of its speed (about 10 seconds for any beast compared with variable times up to 20 seconds for a reciprocating saw depending on the size of the carcasses. Electric circular saws are generally simple in construction and thus have low maintenance requirements and at the same time permit easy and economical blade sharpening. Further there are traditional labour savings in use of a circular saw due to its speed of operation and ease of use which are reflected in labour piece rates applicable to slaughter floor operations. The use of a circular saw necessitates less spreading of the carcass in view of its relatively thin blade compared with those of reciprocating or band saws. Of the prior art saws, only the circular saw has been found particularly suitable for automated systems wherein the saw station is able to traverse with a carcass on a moving conveyor to split the carcass at a set speed.
Although to date electric circular saws have been considered most suitable for automated systems, they suffer a number of serious disadvantages. Electric circular saws of this type generally comprise a pair of 7.5 or 10 horsepower electric motors mounted on either side of the saw blade on a common shaft. Such saws generally weigh in the region of a half tonne which necessitates very complex suspension systems to permit free movement of the saw. The saws are cumbersome to use because of their weight and bulk in addition to the suspension system. The large rotational mass of the saw gives rise to gyroscopic effects which severely limit free movement and the starting and stopping torque applied to the electric motors can cause "kick-back" which is not only difficult to control and dangerous for the saw operator but also causes undue strain on the suspension system. For safety reasons and the sake of efficiency, it is required to be able to stop the rotation of the saw blade immediately after the carcass splitting operation is completed. This is usually achieved by the provision of a plugging contactor which reduces or even reverses the polarity of the motors momentarily. This places enormous strain on the electrical and mechanical components of the saw motors. Other problems associated with electric circular saws are:
1. Limited depth of cut available due to bulk of motors-- this can necessitate use of large blade diameters for large beasts.
2. Very high noise pollution particularly during starting and stopping operation. Under certain cutting conditions, harmonic frequencies of the blade itself can contribute greatly to noise pollution.
3. Lack of speed control to avoid harmonic frequencies in the saw blade. Speed control is also important during washdown and sterilization of the blade. At high speeds wash liquid spray and waste material throw-off can cause a health hazard due to contamination.
4. Sterilization has been considered a problem with this type of saw due to the need to completely contain the saw blade during washdown between carcasses. Complete containment is necessary due to lack of speed control and need to protect motors from ingress of washing liquid.
5. Due to the problems of the weight and bulk of electric circular saws and their suspension systems together with the operational difficulties of "kick-back" and the gyroscopic effects, it has become common practice to mount the saw on a rigid suspension system. The saw is able to travel vertically on the rigid suspension system but it is necessary to carefully align the carcass with the saw blade to permit accurate splitting. This is usually achieved by indexing the carcass to a point adjacent the saw then either stopping the conveyor system or disconnecting the carcass suspension hook from the conveyor, then spreading the hind legs to facilitate easy splitting. After splitting, the carcass sides are then indexed back into the conveyor system by a suitable mechanism.